| Message ID | 20230110173922.265055-19-alex.bennee@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | current maintainer trees (testing/semihosting/plugins) | expand |
On 1/10/23 09:39, Alex Bennée wrote: > From: Emilio Cota<cota@braap.org> > > Fixes the appended use-after-free. The root cause is that > during tb invalidation we use CPU_FOREACH, and therefore > to safely free a vCPU we must wait for an RCU grace period > to elapse. > > $ x86_64-linux-user/qemu-x86_64 tests/tcg/x86_64-linux-user/munmap-pthread > ================================================================= > ==1800604==ERROR: AddressSanitizer: heap-use-after-free on address 0x62d0005f7418 at pc 0x5593da6704eb bp 0x7f4961a7ac70 sp 0x7f4961a7ac60 > READ of size 8 at 0x62d0005f7418 thread T2 > #0 0x5593da6704ea in tb_jmp_cache_inval_tb ../accel/tcg/tb-maint.c:244 > #1 0x5593da6704ea in do_tb_phys_invalidate ../accel/tcg/tb-maint.c:290 > #2 0x5593da670631 in tb_phys_invalidate__locked ../accel/tcg/tb-maint.c:306 > #3 0x5593da670631 in tb_invalidate_phys_page_range__locked ../accel/tcg/tb-maint.c:542 > #4 0x5593da67106d in tb_invalidate_phys_range ../accel/tcg/tb-maint.c:614 > #5 0x5593da6a64d4 in target_munmap ../linux-user/mmap.c:766 > #6 0x5593da6dba05 in do_syscall1 ../linux-user/syscall.c:10105 > #7 0x5593da6f564c in do_syscall ../linux-user/syscall.c:13329 > #8 0x5593da49e80c in cpu_loop ../linux-user/x86_64/../i386/cpu_loop.c:233 > #9 0x5593da6be28c in clone_func ../linux-user/syscall.c:6633 > #10 0x7f496231cb42 in start_thread nptl/pthread_create.c:442 > #11 0x7f49623ae9ff (/lib/x86_64-linux-gnu/libc.so.6+0x1269ff) > > 0x62d0005f7418 is located 28696 bytes inside of 32768-byte region [0x62d0005f0400,0x62d0005f8400) > freed by thread T148 here: > #0 0x7f49627b6460 in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:52 > #1 0x5593da5ac057 in cpu_exec_unrealizefn ../cpu.c:180 > #2 0x5593da81f851 (/home/cota/src/qemu/build/qemu-x86_64+0x484851) > > Signed-off-by: Emilio Cota<cota@braap.org> > Message-Id:<20230109224954.161672-2-cota@braap.org> > Signed-off-by: Alex Bennée<alex.bennee@linaro.org> > --- > accel/tcg/tb-jmp-cache.h | 1 + > accel/tcg/cpu-exec.c | 3 +-- > cpu.c | 11 ++++++++++- > 3 files changed, 12 insertions(+), 3 deletions(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
diff --git a/accel/tcg/tb-jmp-cache.h b/accel/tcg/tb-jmp-cache.h index ff5ffc8fc2..b3f6e78835 100644 --- a/accel/tcg/tb-jmp-cache.h +++ b/accel/tcg/tb-jmp-cache.h @@ -18,6 +18,7 @@ * a load_acquire/store_release to 'tb'. */ struct CPUJumpCache { + struct rcu_head rcu; struct { TranslationBlock *tb; #if TARGET_TB_PCREL diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index 356fe348de..6bd29227f3 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -1064,13 +1064,12 @@ void tcg_exec_realizefn(CPUState *cpu, Error **errp) /* undo the initializations in reverse order */ void tcg_exec_unrealizefn(CPUState *cpu) { - qemu_plugin_vcpu_exit_hook(cpu); #ifndef CONFIG_USER_ONLY tcg_iommu_free_notifier_list(cpu); #endif /* !CONFIG_USER_ONLY */ tlb_destroy(cpu); - g_free(cpu->tb_jmp_cache); + g_free_rcu(cpu->tb_jmp_cache, rcu); } #ifndef CONFIG_USER_ONLY diff --git a/cpu.c b/cpu.c index 4a7d865427..21cf809614 100644 --- a/cpu.c +++ b/cpu.c @@ -176,11 +176,20 @@ void cpu_exec_unrealizefn(CPUState *cpu) vmstate_unregister(NULL, &vmstate_cpu_common, cpu); } #endif + + /* Call the plugin hook before clearing cpu->cpu_index in cpu_list_remove */ if (tcg_enabled()) { - tcg_exec_unrealizefn(cpu); + qemu_plugin_vcpu_exit_hook(cpu); } cpu_list_remove(cpu); + /* + * Now that the vCPU has been removed from the RCU list, we can call + * tcg_exec_unrealizefn, which may free fields using call_rcu. + */ + if (tcg_enabled()) { + tcg_exec_unrealizefn(cpu); + } } /*